Resistance unit.



G. E. STEVENS.

RESISTANCE um.

I APYLIGATION FILED 00'1.2, 1908. I 1 22,897, Patented Apr; 9, 191.2.

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' GEUHGE' E. ETEYENS' 1 UNITED STATES PATENT OFFICE.

ononon nsums, of mm, MASSACHUSETTS, assrsnon r0 GENERAL nnncrnro comm, A COMB-ALBION OF NEW YORK.

nasrsrancn UNIT.

Specification of Letters Patent. Application filed October 2, 1908. Serial No. 455,893.

Patented Apr. 9, 1912.

To all whom'i't Be itknown that I, GEORGE S'ravnNs,

a citizen of the United States, "residing at Lynn, countyof 'Essex, State of Massachu setts, have invented certain new and useful Improvements in Resistance Units, of which the following" is a specification.

This invention relates to electric resistance units and has for its object the rovision of a device of-this character w ich the two portions of the spiral being'separated by a thin strip, as for instance, by insulating material. The spirals are punched or stamped out of metal by a single operation. This forms two-spirals connected .together at their inner ends andhaving their corresponding turns adjacent. Strips ofmica are then inserted between the two spirals so as -to separate them and at the same time leave them as near together as possible, so as to make the unit a very thin one. This construction makes a very eificient arrangement possible and adapts it in a peculiar manner to theme of two heats.

In the accompanying drawing, in which I have shown my invention embodied in concrete form, Figure 1 represents a plan view of the heating unit after it has been punched but before the s irals have been separated; Fig. 2 shows t e unit with the mica strips between the spirals; Fig. 3 shows an end view of the unit represented in Fig. 2; Fig. 4 shows a diagram of the circuit connections through the spirals; and Fig. 5 shows the punch and die employed in forming these units.

Referring to these drawings, 1 represents a sheet of thin resistance metal which has been punched out to form two spirals. This metal may be of any suitable composition, but I have found that the material disclosed in thepatent of, Dempster, No. 901,428;

forms two spirals 13 and 14, as shown in central portion 15. The consecutive turns are then separated as shown in Fig. 2 by the mica vst ri s 16, so that one spiral is on one side of the-strips =and the other spiral -'on the other side. The metal'may be cut to form the spirals by means of the punch and die shown in Fig. 5, in which the spirals are formed in the shape of a cone so as to constitute a spiral thread. Any other suitable means, however, for forming the. unit will be utilized without departing from the spirit of my invention. In Fig. 4 I have shown. the circuitconnect-ions of the two spirals. It will be seen that by connecting Figs. and 3, connected together at the v the center of the spirals with one side of the circuit, and the two ends ofthe spirals with the other side, by means of a double pole switch 17 the spirals will be arranged in series or in parallel; When contact is made with studs 19 and 20 andcontact 21, a circuit is closed from the positive main to the center of the spirals, thence to the stud 20 and the contact 21. If, however, the switch is moved so as to engage only stud 20 and contact 21, current will pass through the positive main to the contact 20, thence through the two spirals in series back to the contact 21.

'It will be seen that the unit is particularly Well adapted for multiple heat arrangement and is at the same timean exceedingly simple and convenient form for use with heating vessels of the cylindrical .type.- Its extreme thinness, moreover, permits of its being placed in intimate thermal relation with the device to be heated. The resistance metal may be insulated by means of a thin film or not, as desired.

It should be understood that while I 111m; described my invention as constructed in' a specific manner, I do not limit my invention thereto, as various other methods will suggest themselves to those skilled in the art without departing from the spirit of my invention,,the scope of which is set forth in the annexed claims.

What I claim as, new and desire to secure by Letters Patent of the United States, is,

1. An electric heating unit comprising a continuous resistance conductor formed into a plurality of spirals connected at theoenter andlying in different planes, and a spacing member between said spirals}.- A

2. An electric heating unit' corflprising a.

continuous conductor formed into. a plnrality of parallel spirals and a spacing strip between said spirals.

3. An electric heating unit comprising a flat resistance conductor doubled edgewise on itself and shaped to form two s irals and a spacing strip between said spira s.

4. An electric heating unit comprising a thin sheet of resistance metal cut to form concentric spirals joined at the center and a spacing strip between said spirals. Y

5'. An electric heating unlt comprising a thin sheet of resistance metal cut to form concentric spirals joined at one end and Copies 0! this patent-may be obtained for lying in difi'erent planes, and a spacing 5 member between said spirals.

6. An electric heating unit comprising a thin sheet of resistance metal cut to form concentric spirals joined at one end and a spacing strip between said spirals.

In witness whereof, I have hereunto set my hand this thirtieth day of September, 1908.

GEORGE E. STEVENS.

Wit-nessesz' JOHN A. MCMANUS, Jr., HENRY O. WESTENDAYS.

five cent: eacl by addressing the "Commissioner 6! Patents, Washington, D. 0. 

